In recent years pneumatic delivery systems have been employed in farm vehicles to deliver seed, fertilizer and herbicides to planters and tool bars. One such system is shown in U.S. Pat. No. 4,473,016, issued to Gust. In this system, a tractor pulls a particulate feeder or "cart" typically having two or three separate hoppers terms "bin" and "hopper" are synonyms and are used interchangeably herein) The cart, depending upon its size, may have three or four wheels and a longitudinal tube extending its length. Each hopper is typically equipped with a rotating metering cylinder disposed between that hopper and the tube to meter particulate matter (seed, fertilizer or herbicides) into the tube when the cylinder rotates. An engine or hydraulic motor on the cart drives a fan that is pneumatically coupled to the tube to blow air through the tube. The air flow in the tube accelerates the particulate matter and blows it into a series of pneumatic manifolds on the planter or tool bar (also towed by the tractor) that pneumatically distribute the particulate matter equally to a plurality of ground openers.
Seed and fertilizer may be distributed simultaneously to the tool bar by placing seed in one hopper and fertilizer in another, both of which are then metered into the tube to be sent to the pneumatic manifold distribution system on the planter. There are several drawbacks to this method, however. First, since the seed is mixed with the fertilizer in the tube, seed may be burned by the fertilizer. To prevent this in other embodiments, the tube has been subdivided into two separate air paths by placing a partition or "ribbon" down the length of the tube. The seed is then metered into one-half of the tube, and the fertilizer is metered into the other half of the tube. At the end of the tube, each of these separate partitions is directed to a separate pneumatic distribution system on the planter, rather than distributing a seed-chemical mix in a single common manifold system such as that shown in the Gust reference.
Even a dual manifold and partition arrangement has drawbacks, however. Using air in a manifold system to evenly distribute the seeds may be acceptable for durable seeds, such as wheat, but can cause problems for seeds such as canola and corn. When a manifold distribution system is used with these grains, they suffer damage when they impact the top of the manifolds and suddenly reverse direction to proceed down the tubes extending radially away from the manifold. In addition, the air flow in a manifold distribution system must be high to lift the grains up the manifolds and to cause sufficiently random turbulence to distribute seeds evenly to each of the rows. This commonly results in damage to 1-25% of the seeds.
There are additional disadvantages to a manifold distribution system for crops that require very low application rates. For example, canola, corn and sunflower seeds are deposited at a rate of between 4 and 25 pounds of seed per acre. When a metering cylinder at the bottom of a hopper is used to meter seed at this rate, the flutes must be made especially small and carefully tapered to insure that seed is introduced into the longitudinal tube evenly over time. Also, the manifold system is not able to distribute the seeds evenly when only small amounts are being applied.
It is possible to accurately meter seed flow with less damage by eliminating the manifold arrangement for pneumatically distributing seeds and replacing it with one or more mechanical metering systems such as the Cyclo unit illustrated in U.S. Pat. No. 4,519,525. In such a system, the air velocity can be reduced since air is used merely to deliver seed to the Cyclo unit and the Cyclo unit mechanically distributes seeds to each row. Providing two mechanical metering devices in series (the rotating cylinder and Cyclo unit) has drawbacks, however. The two metering systems are difficult to synchronize. Since one feeds the other, a lack of synchronization can overfill or underfill the Cyclo unit, potentially plugging it, or starving it for seeds, respectively. To prevent this problem, some method of controlling the metering rate to the Cyclo unit must be provided. Experiments have been conducted in which a sensor on the Cyclo drum signals the metering cylinder on the cart to turn on and off. Such methods, however, require the addition of a motor or other controllable apparatus to rotate the metering cylinder, and also a sensor at each Cyclo unit to sense its level of seed.
What the Applicants propose is a new apparatus for supplying grain from a portable grain bin to a grain meter that will reduce or eliminate the above disadvantages.